First use a CIS tool to measure the main pressure. Then use that tool to measure the difference of .4 bar
Next use an ammeter to measure the current draw to the EHA. To do this, disconnect the EHA harness then connect one pin of the EHA to one side of the harness while you stick the ammeter between the other side of the harness connector to the other EHA pin. ZERO + or - 1mA will be acceptable.